Different SIM designs are used in industry, but the classic design is the 2FF SIM, or plug-in SIM card. With its dimensions of 2.5 cm by 1.5 cm it is especially popular in the M2M sector, while the micro SIM, which at 1.5 cm by 1.2 cm edge length is even more compact for use in M2M applications. The micro SIM, also known as the 3FF SIM, is the most common type of SIM used in smartphones.
The two plug-in SIMs have a major advantage in that they can be fitted simply and swiftly into M2M applications of all kinds and are ideally suited for use in conventional conditions. Plug-in SIMs also enable low-cost production of M2M solutions that are required in small numbers and are suitable for limited use in extreme conditions. In both, the transitions between the SIM contact surfaces and the contact springs of the rest of the electronics are seen as potential sources of faults.
The MFF SIM: A tough customer
Shocks, humidity and corrosion can interrupt contact between the circuit board and the SIM card, impairing an M2M application’s failure safety. Carriers who design rugged devices for mobile M2M use special M2M SIM chips, known as MFF SIMs, in their M2M solutions. Depending on the type used, these SIMs are impervious to temperatures of -40°C to over 100°C (-40°F to 212°F).
Furthermore, MFF SIMs are smaller than plug-in SIMs and can be inserted by pick and place in automated production lines. In this way, robust and compact M2M solutions can be manufactured in bulk. An MFF SIM with its corrosion-resistant contacts is permanently integrated into the M2M electronics – in other words, soldered onto the circuit board. This makes it more robust and longer lasting than solutions that use plug-in SIMs – even in terms of write and erase cycles.
The SIM memory is accessed during each and every network authentication process and ages accordingly. MFF SIMs are designed for up to 500,000 accesses, or five times as many as plug-in SIMs, and their permanent integration into the electronics provides protection from manipulation and theft.
As new innovations in ruggedized SIM chips make reliable M2M communications possible in extreme conditions, expect to see more development of applications to make automation more common. Automated processes in extreme locations will mean a safer experience for human users, along with greater efficiencies and cost savings.
About the Author
Jürgen Hase, Vice President M2M Competence Center, Deutsche Telekom AG, joined Deutsche Telekom AG in 2011 to head the M2M Competence Center. Within Deutsche Telekom, he is responsible for the international M2M business. Jürgen has worked more than 20 years in the telecommunications industry and in the M2M sector. He is also Chairman of the M2M alliance.
This article originally appeared on EDN.